Arachniodes hehaii Li Bing Zhang, N.T. Lu & X.F.Gao, 2019

Lu, Ngan Thi, Gao, Xin-Fen & Zhang, Li-Bing, 2019, Arachniodes hehaii (Dryopteridaceae), a new fern from Guizhou, China, Phytotaxa 392 (1), pp. 84-86 : 84-85

Arachniodes hehaii Li Bing Zhang, N.T. Lu & X.F.Gao , sp. nov. Fig. 1 .

Type:— CHINA. Guizhou Province: Libo County, Dongtang Xiang, Xinjie Cun, Jiugong Zu, at the entrance of the Wangyi Cave in forest, elev. 700 m, 28 October 2008, Li Bing Zhang & Hai He 848 (holotype CDBI-0250381!, isotype CTC).

Diagnosis:—This species is most similar to Arachniodes chinensis ( Rosenstock 1914: 130) Ching (1962: 257) in having dense appressed subulate scales on upper stipes and rachises, laminae 2-pinnate-pinnatifid, lamina apex abruptly narrowed, 3 pairs longest pinnae at the lamina base, basal pinnae obliquely deltoid and distal pinnae lanceolate, the lowest pinnae often sterile, but A. hehaii has stipe scales reddish brown, laminae broader, ovate-deltoid, lamina apex caudate-acuminate, and indusia often thicker, while A. chinensis has stipe scales blackish, laminae narrower, ovate-oblong, lamina apex long-acuminate, and indusia membranous to firmly membranous.

Rhizome unseen. Frond approximates, ca. 75 cm; stipe longer than lamina, stramineous, ca. 38 cm, 1 mm in diam., lower parts densely scaly; scales reddish brown, linear-lanceolate or subulate, 2–8 × 0.1–1.1 mm, entire; upper parts with linearfiliform or appressed subulate scales, 1.5–9 × 0.06–0.3 mm, rounded-based, entire to sparsely dentate, at base with hairlike outgrowths; lamina 2-pinnate-pinnatifid, dull green when dried, deltoid-ovate, ca. 29 × 19 cm, thickly leathery, apex abruptly narrowed, caudate-acuminate, rachis scaly as distal portion of stipe, adaxially sparser; pinnae ca. 13 pairs, therein 3 basal pairs longest, alternate and lowest pair opposite, stalk of basal pinnae ca. 1 cm, those of upper pinnae shorter; lowest pinnae obliquely deltoid, to 20 × 8.5 cm, base asymmetric, broadly cuneate, apex acuminate; lateral pinnae lanceolate, 4–14 × 2–3.3 cm, base cuneate, apex long-acuminate; primary pinnules ca. 16 pairs, stalk of basalmost pinnules ca. 0.3 cm, upper pinnules sessile, basal pair elongated (basiscopic one longer, to 4.5 × 1.4 cm), lanceolate, oblong, base cuneate, apex acuminate; secondary pinnules shortly stalked or sessile, oblong or slightly falcate, ca. 4 × 0.5 cm, base cuneate, apex acute or obtuse, margins aristate; upper pinnae gradually reduced; axes and veins of ultimate segments with minute (blackish) brown, appressed subulate scales abaxially, glabrous adaxially. Sori 8–19 per ultimate pinnule, middle to submarginal, 0.7–1 mm in diam., lowest pinnae often sterile; indusia ca. 0.2 mm in diam., black, firmly membranous, margins entire. Spores unseen.

Etymology:— In honor of Prof. Hai He, a pteridologist and ecologist based at CTC, for his contributions to the taxonomy of Arachniodes ( He & Wu 1996, He 2004, He et al. 2013). He is also one of the two collectors of the type material.

Geographical distribution:— This species is currently known only from the type locality in southern Guizhou, China. It could occur in the neighboring areas.

Taxonomic notes:— Our molecular data resolved Arachniodes hehaii as sister to a clade containing A. attenuata Ching (1986: 2) , A. chinensis , A. jinpingensis Hsieh (1983: 55) , A. simplicior ( Makino 1901: 65) Ohwi (1962: 76) , and A. yasu-inouei Kurata (1968: 6) , but this sister relationship received only weak support ( Lu et al. 2019), suggesting that the relationships of A. hehaii were not clear. Morphologically, A. hehaii resembles A. chinensis (type: Guizhou, China), but they are obviously different (see above). In the field the types of A. hehaii were tentatively identified as A. aristata ( Forster 1786: 82) Tindale (1961: 89) because of the caudate-acuminate lamina apex, ovate-deltoid lamina shape, and long-aristate teeth, but our phylogenetic work showed that the Asian material and the relevant material from Australian/Pacific islands belong to distinct lineages and so, should represent different species ( Lu et al. 2019), as hypothesized by Sledge (1973).

Although the types were collected from a cave entrance, we do not think that Arachniodes hehaii is a cave endemic like many other cave species of Polystichum Roth (1800: 31 ; Dryopteridaceae ) often endemic to single caves (e.g., Han et al. 2016, 2018). The accurate distribution of A. hehaii is still unclear. Presumably the new species also occurs in neighboring northern Guangxi, but more investigations are needed.

Figures

FIGURE 1. Arachniodes hehaii,—A. Frond.—B & C. Portions of pinnae showing segment margins, veins, and sori.—D. Lower part of stipe showing scales.—E. Upper part of stipe showing appressed subulate scales.—F. Scales from stipe base.—G. Scales from upper part of stipe.—H. Rachis scales.—I. Indusia.—J. Portion of lamina showing microscales and sori (based on the holotype).